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PubMed2005

Micronucleus induction in erythrocytes of the Hyla pulchella tadpoles (Amphibia: Hylidae) exposed to insecticide endosulfan.

Endosulfan is a synthetic chlorinated and environmental genotoxic pesticide used worldwide for crop production. We used the micronucleus test in erythrocytes of Hyla pulchella tadpoles in order to develop an experimental model for detecting genotoxic effects of the synthetic chlorinated cyclodiene endosulfan. The frequency of micronuclei was examined in blood smears obtained from tadpoles exposed in vivo to three different concentrations 2.5, 5, and 10 microg/l of the compound and fixed at two sampling times 48 and 96 h. As a positive control larvae were exposed to 40 mg/l of cyclophosphamide. Results obtained here demonstrated the genotoxic effects of the commercial formulation endosulfan in the experimental model assayed.

Animals↗
PubMed2004

Distribution of alpha7 and alpha4 nicotinic acetylcholine receptor subunits in several tissues of Triturus carnifex (Amphibia, Urodela).

The distribution of neuronal and non-neuronal mRNAs for alpha7 and alpha4 nicotinic acetylcholine receptor subunits was investigated in Triturus carnifex tissues using the in situ hybridization approach. The findings reveal a composite pattern of expression only partially overlapping for the two subunits; subunit alpha7 seems to be expressed widely throughout nervous, gastrointestinal and skin tissues, while alpha4 is present in a restricted number of cells of nervous and gastrointestinal tissue. We also found a specific pattern for each subunit; alpha7 and alpha4 associated exclusively to the epidermal glands and hypophysis, respectively; this is probably due to alternative roles that nicotinic acetylcholine receptors play in regulating physiological functions of non-neuronal amphibian tissues, rather than as mere neurotransmitters in the nervous system.

Animals↗
PubMed2005

Complex secretory products in the oviduct of the plethodontid salamander Bolitoglossa dofleini (Amphibia, Urodela).

The ultrastructure of the secretory granules in the cells of the subdivisions of the oviduct in the neotropical plethodontid salamander Bolitoglossa dofleini was studied by transmission electron microscopy. In addition, we applied the cationic dye Cuprolinic Blue (CB) at different electrolyte concentrations to demonstrate proteoglycans, and the pyrogallol red-copper (PR-C) method to stain proteins at the ultrastructural level. The entire oviduct is lined by a simple epithelium that contains ciliated and microvillous cells in the first subdivision, the aglandular pars recta; microvillous cells show a moderate secretory activity. The following pars convoluta is differentiated into five glandular subdivisions and the aglandular "uterine portion". Especially in the glandular parts, the epithelium is arranged in longitudinal folds. At their crests ciliated and microvillous cells similar to those in the pars recta occur. Gland cells are crowded with secretory granules that differ in their structural complexity (with and without electron-dense spheres or masses; elaborated, homogeneous or granular matrix; spherical; distorted) along the various subdivisions. Further, as suggested by the CB-technique, the cranial subdivisions contain large amounts of sulphated proteoglycans that decrease in the caudal direction. Carboxylated proteglycans appear to be present in all subdivisions examined. Electron-dense spheres of secretory granules are largely free of CB-precipitates, but stain more or less intensely with PR-C. The ultrastructure of the pars recta, and especially the "uterine portion" indicates transporting capability. The epithelial cells of the "uterus" have coated pits and a considerable amount of lysosome-like bodies.

Animals↗
PubMed2004

Endemic ranid (Amphibia: Anura) genera in southern mountain ranges of the Indian subcontinent represent ancient frog lineages: evidence from molecular data.

The geological history of the Indian subcontinent is marked by successive episodes of extensive isolation, which have provided ideal settings for the development of a unique floral and faunal diversity. By molecular phylogenetic analysis of a large set of ranid frog taxa from the Oriental realm, we show that four genera, now restricted to torrential habitats in the Western Ghats of India and the central highlands of Sri Lanka, represent remnants of ancient divergences. None of three other biodiversity hotspots in the Oriental mainland were found to harbour an equivalent level of long-term evolutionary history in this frog group. By unceasingly providing favourable humid conditions, the subcontinent's southern mountain ranges have served as refugia for old lineages, and hence constitute a unique reservoir of ancient ranid endemism.

Animals↗
PubMed2005

Phylogenetic relationships of Hynobius naevius (Amphibia: Caudata) as revealed by mitochondrial 12S and 16S rRNA genes.

Using mitochondrial 12S and 16S rRNA sequences, we investigated phylogenetic relationships among populations of the endemic Japanese salamander Hynobius naevius. Monophyly of this species was recovered only in the maximum parsimony tree and was unresolved in maximum likelihood and Bayesian trees. Instead the following four haplotype clades consistently emerged clearly: Clade 1 from northwestern Kyushu, Clade 2 from Chugoku and northeastern Kyushu, Clade 3 from western Shikoku and Kyushu, and Clade 4 from Chubu-Kinki and central-eastern Shikoku. Of these, Clades 1 and 2, and Clades 3 and 4, respectively, correspond to Groups A and B previously recognized from the analyses of allozyme data in this species, but monophyly of these groups was not strongly supported. Unlike the previous results, the western and eastern samples from Shikoku did not form a clade, and were grouped with Kyushu-B in Clade 3 and Chubu-Kinki in Clade 4, respectively. The reason for this conflict between mtDNA and allozyme results is unknown, but might be related to retention of ancestral mtDNA polymorphism in Shikoku populations. Nearly simultaneous divergence of as many as four lineages in wide-ranging H. naevius is inferred for the late Miocene-Pliocene history of this taxon.

Animals↗
PubMed2006

Phylogenetic relationships of Oriental torrent frogs in the genus Amolops and its allies (Amphibia, Anura, Ranidae).

We investigated the phylogenetic relationships among 20 species of Oriental torrent frogs in the genus Amolops and its allies from China and Southeast Asia based on 1346-bp sequences of the mitochondrial 12S and 16S rRNA genes. Oriental species of the tribe Ranini form a monophyletic group containing 11 clades (Rana temporaria + Pseudoamolops, R. chalconota, four clades of Amolops, Meristogenys, three clades of Huia species, and Staurois) for which the phylogenetic relationships are unresolved. The genus Amolops consists of southern Chinese, southwestern Chinese, Thai, and Vietnamese-Malaysian lineages, but their relationships are also unresolved. The separation of southern and southwestern lineages within China conforms to previous morphological and karyological results. Species of Huia do not form a monophyletic group, whereas those of Meristogenys are monophyletic. Because P. sauteri is a sister species of R. temporaria, distinct generic status of Pseudoamolops is unwarranted.

Animals↗
PubMed2006

A molecular assessment of phylogenetic relationships and lineage accumulation rates within the family Salamandridae (Amphibia, Caudata).

We examine phylogenetic relationships among salamanders of the family Salamandridae using approximately 2700 bases of new mtDNA sequence data (the tRNALeu, ND1, tRNAIle, tRNAGln, tRNAMet, ND2, tRNATrp, tRNAAla, tRNAAsn, tRNACys, tRNATyr, and COI genes and the origin for light-strand replication) collected from 96 individuals representing 61 of the 66 recognized salamandrid species and outgroups. Phylogenetic analyses using maximum parsimony and Bayesian analysis are performed on the new data alone and combined with previously reported sequences from other parts of the mitochondrial genome. The basal phylogenetic split is a polytomy of lineages ancestral to (1) the Italian newt Salamandrina terdigitata, (2) a strongly supported clade comprising the "true" salamanders (genera Chioglossa, Mertensiella, Lyciasalamandra, and Salamandra), and (3) a strongly supported clade comprising all newts except S. terdigitata. Strongly supported clades within the true salamanders include monophyly of each genus and grouping Chioglossa and Mertensiella as the sister taxon to a clade comprising Lyciasalamandra and Salamandra. Among newts, genera Echinotriton, Pleurodeles, and Tylototriton form a strongly supported clade whose sister taxon comprises the genera Calotriton, Cynops, Euproctus, Neurergus, Notophthalmus, Pachytriton, Paramesotriton, Taricha, and Triturus. Our results strongly support monophyly of all polytypic newt genera except Paramesotriton and Triturus, which appear paraphyletic, and Calotriton, for which only one of the two species is sampled. Other well-supported clades within newts include (1) Asian genera Cynops, Pachytriton, and Paramesotriton, (2) North American genera Notophthalmus and Taricha, (3) the Triturus vulgaris species group, and (4) the Triturus cristatus species group; some additional groupings appear strong in Bayesian but not parsimony analyses. Rates of lineage accumulation through time are evaluated using this nearly comprehensive sampling of salamandrid species-level lineages. Rate of lineage accumulation appears constant throughout salamandrid evolutionary history with no obvious fluctuations associated with origins of morphological or ecological novelties.

Animals↗
PubMed1996

Helminth infracommunities in Litoria genimaculata (Amphibia:Anura) from Birthday Creek, an upland rainforest stream in northern Queensland, Australia.

The helminth fauna of Litoria genimaculata, a rainforest frog from northern Queensland, was quantified from 53 adult male frogs collected at monthly intervals between April 1990 and March 1991. The helminth fauna of this species was depauperate (6 species: Mesocoelium sp., Parapolystoma bulliense, Austraplectana sp., Onchocercidae gen. sp., Cosmocerca sp. and an unidentified nematode larva). The most commonly encountered species was P. bulliense, but the intestinal infracommunity was dominated by the digenean Mesocoelium sp. Fifty-five per cent of frogs were infected with only 1 helminth species and only 1 frog had more than 2 species, resulting in low diversity values. These results support previous studies which indicate that amphibians have depauperate helminth communities.

Animals↗
PubMed1985

A neural model of interactions subserving prey-predator discrimination and size preference in anuran amphibia.

The model described is an extension of a previous model of the optic tectum (Arbib & Lara, 1982; Lara, Arbib & Cromarty, 1982; Lara & Arbib, 1982) and takes into consideration anatomical, physiological and behavioral studies in anurans, as well as earlier modelling efforts (Ewert & Von Seelen, 1974; Didday, 1976). Computer simulations were conducted to analyze how interactions among retina, optic tectum and pretectum may give frogs and toads the ability to discriminate between prey and predator stimuli. Results from simulations have allowed us to reproduce empirical observations, to suggest new experiments, and to postulate what neural mechanisms might be involved in some phenomena related to prey-catching orienting behavior, with direction invariance of prey-predator recognition being a consequence of tectal architecture, and size preference and response latency depending on the motivational state of the animal.

Animals↗
PubMed2002

The ultrastructure of the spermatozoa of Epipedobates flavopictus (Amphibia, Anura, Dendrobatidae), with comments on its evolutionary significance.

We describe, for the first time, the spermatozoon ultrastructure of a dendrobatid frog, Epipedobates flavopictus. Mature spermatozoa of E. flavopictus are filiform, with a moderately curved head and a proportionally short tail. The acrosomal vesicle is a conical structure that covers the nucleus for a considerable distance. A homogeneous subacrosomal cone lies between the acrosome vesicle and the nucleus. The nucleus contains a nuclear space at its anterior end, and electron-lucent spaces and inclusions. No perforatorium is present. In the midpiece, the proximal centriole is housed inside a deep nuclear fossa. Mitochondria are scattered around the posterior end of the nucleus and inside the undulating membrane in the anterior portion of the tail. In transverse section the tail is formed by an U-shaped axial fiber connected to the axoneme through an axial sheath, which supports the undulating membrane. The juxta-axonemal fiber is absent. The spermatozoon of E. flavopictus has several characteristics not observed before in any anurans, such as a curved axial fiber, absence of a juxta-axonemal fiber, and presence of mitochondria in the typical undulating membrane. Our results endorse the view that, in anurans, the conical perforatorium and subacrosomal cone are homologous and that Dendrobatidae should be grouped within Bufonoidea rather than Ranoidea.

Acrosome↗
PubMed2003

Ultrastructural patterns of secretory activity in poison cutaneous glands of larval and juvenile Dendrobates auratus (Amphibia, Anura).

A transmission electron-microscope study has been performed on larval and juvenile skin of the Central American arrow-frog Dendrobates auratus to investigate early secretory processes and maturational changes in the serous (poison) glands. Poison biosynthesis involves the endoplasmic reticulum (both smooth and rough types), as well as Golgi stacks which release early serous product as secretory vesicles (or pre-granules). These vesicles contain fine-grained material, along with single electron-opaque bodies, spheroidal in shape, that accompany the grained product throughout its post-Gogian, maturational change. The first steps of this process involve condensation and lead to the formation of secretory granules with a glomerular-like substructure, resulting from a thick, random aggregation of rods (secretory granule subunits). Advanced maturational activity causes the loss of peculiar granule substructure: the dense bodies split into fragments, whereas the thick glomerular arrangement becomes looser, until the secretory product changes into a dispersed material. This ultrastructural study revealed biosynthesis and maturation processes in close sequence, suggesting the poison of D. auratus contains proteins and/or peptides as well as lipophilic compounds. Molecules of both these classes are known to perform several roles relevant to survival strategies in extant anurans. Furthermore, the ephemeral granules with a glomerular-like substructure detected in tadpoles and froglets exhibit the complex patterns of mature poisons in adult specimens of other anurans: Hylidae and related families. This agrees with current trends in the taxonomy of these advanced frogs and underlines the pertinence of an ontogenetic approach in investigating anuran phylogenesis.

Amphibians↗
PubMed1999

Indirect cardiotoxic activity of the caecilian Siphonops paulensis (Gymnophiona, Amphibia) skin secretion.

The skin secretion of the caecilian S. paulensis has an indirect cardiotoxic effect. It induces a rapid blockage of electrical activity and subsequent diastolic arrest on in situ toad heart preparations. This action is not blocked by atropine and is therefore not mediated through a cholinergic mechanism. In addition, S. paulensis skin secretion is ineffective in inducing any response in isolated perfused toad heart assay, in the spontaneously beating isolated toad atria or in the electrically driven toad ventricle strip. These results, and the observation that S. paulensis skin secretion exhibits an hemolytic activity ([Schwartz, E. F., Schwartz, C. A., Sebben, A., Mendes E. G. (1997) Cardiotoxic and hemolytic activities on the caecilian Siphonops paulensis skin secretion. J. Venom. Anim. Toxins 3(1), 190]), suggest that the skin secretion cardiotoxicity could be mediated through an endogenous agent. The cardiotoxic action of S. paulensis skin secretion was investigated in isolated toad cardiac tissues in the presence of toad red blood cells (TRBC). In both atria and ventricle it evoked the same responses observed in the in situ heart. The potassium concentrations of the suspending media, as determined by atomic absorption spectroscopy were 9.5 and 11.7 times greater, respectively, in the presence of TRBC than in its absence. Given that increased levels of potassium also showed a negative inotropic effect in the isolated ventricle strip, the action of the skin secretion was attributed to the hemolytic activity, which causesan increase in K+ concentration of the medium.

Amphibian Venoms↗
PubMed1999

Secretory polymorphism and serous cutaneous gland heterogeneity in Bufo granulosus (Amphibia, Anura).

Three types of secretory products (a, b and c) in the poison glands of the Argentine toad Bufo granulosus have been detected under light microscope. The type a secretory product consists of granules of homogeneous density, type b of vesicles with a translucent compartment and type c of granules of varying density. Subsequent transmission electron microscope analysis disclosed obvious similarities in the secretory pathways of type a and c granules; the differences detected under light microscope are due to the functional phases observed. On the contrary, production of type b secretory vesicles involves a distinctive pathway. Therefore, two classes of glands (I and II) have been identified. Glands of the first class are typical of bufonid toads and produce granules provided with repeating substructure; glands of the second class, which manufacture a lucent product, are unusual in the family Bufonidae. Ultrastructural differences, consistent with the two gland classes, have also been described in the myoepithelia. The myocytes ensheathing class I secretory units possess striking cytoskeletal specializations, whereas those of class II glands are rich in sarcoplasmic reticulum. The distinctive ultrastructural traits detected in these myoepithelial cells have been compared with the results of previous studies on the dimorphic serous glands of Bombina. Findings point to the use of pharmacological treatment on the skin of anurans with different classes of serous glands to elicit differential secretory discharge.

Animals↗
PubMed1982

Localization of calcium in fibrocytes associated with the "substantia amorpha" in the skin of toad, Bufo bufo (L.) (Amphibia, Anura).

Using the potassium pyroantimonate-technique in the fibrocytes associated with the calcium-containing granules of the substantia amorpha within the dermis of Bufo bufo numerous electron-dense deposits have been observed. Reaction product lies in the mitochondria, at the plasma membranes and in various vesicular structures. X-ray microanalysis confirmed that pyroantimonate was predominantly associated with calcium. It is suggested that certain organelles of the fibrocytes are capable of sequestering calcium ions and that the fibrocytes are involved in the Ca-metabolism of the substantia amorpha.

Animals↗